Infrared imaging microscope using tunable laser radiation

ABSTRACT

An imaging microscope (12) for generating an image of a sample (10) comprises a beam source (14) that emits a temporally coherent illumination beam (20), the illumination beam (20) including a plurality of rays that are directed at the sample (10); an image sensor (18) that converts an optical image into an array of electronic signals; and an imaging lens assembly (16) that receives rays from the beam source (14) that are transmitted through the sample (10) and forms an image on the image sensor (18). The imaging lens assembly (16) can further receive rays from the beam source (14) that are reflected off of the sample (10) and form a second image on the image sensor (18). The imaging lens assembly (16) receives the rays from the sample (10) and forms the image on the image sensor (18) without splitting and recombining the rays.

RELATED INVENTION

This application is a continuation application of U.S. application Ser.No. 15/209,596, filed Jul. 13, 2016, and entitled “INFRARED IMAGINGMICROSCOPE USING TUNABLE LASER RADIATION”. As far as permitted, thecontents of U.S. application Ser. No. 15/209,596 are incorporated hereinby reference.

U.S. application Ser. No. 15/209,596 is a continuation application ofU.S. application Ser. No. 14/353,487, filed Apr. 22, 2014 and entitled“INFRARED IMAGING MICROSCOPE USING TUNABLE LASER RADIATION”. As far aspermitted, the contents of U.S. application Ser. No. 14/353,487 areincorporated herein by reference.

U.S. application Ser. No. 14/353,487 is a 371 of PCT/US12/61987, filedOct. 25, 2012 and entitled “INFRARED IMAGING MICROSCOPE USING TUNABLELASER RADIATION”. As far as permitted, the contents of PCT/US12/61987are incorporated herein by reference.

PCT/US12/61987 claims priority on U.S. Provisional Application Ser. No.61/551,147, filed Oct. 25, 2011 and entitled “INFRARED IMAGINGMICROSCOPE USING TUNABLE LASER RADIATION FOR SPECTROSCOPIC ANALYSIS OFSAMPLES”. As far as permitted, the contents of U.S. ProvisionalApplication Ser. No. 61/551,147 are incorporated herein by reference.

GOVERNMENT SPONSORED DEVELOPMENT

The U.S. Government has rights in this invention pursuant to contractnumber NSF SBIR Phase I Award No. 11-1046450 with the National ScienceFoundation.

BACKGROUND

Microscopes are often used to analyze a sample in order to evaluatecertain details and/or properties of the sample that would not otherwisebe visible to the naked eye. Additional information on the chemicalproperties of the sample can be obtained by illuminating and observingthe sample with distinct wavelengths of monochromatic laser radiation.Samples that can be analyzed this way include human tissue, explosiveresidues, powders, liquids, solids, inks, and other materials. A humantissue sample may be analyzed for the presence of cancerous cells and/orother health related conditions. Other materials may be analyzed for thepresence of explosive residues and/or other dangerous substances.

SUMMARY

The present invention is directed toward an imaging microscope forgenerating an image of a sample, the imaging microscope comprising abeam source, an image sensor and an imaging lens assembly. The beamsource emits a temporally coherent illumination beam, the illuminationbeam including a plurality of rays that are directed at the sample. Theimage sensor converts an optical image into an array of electronicsignals. In one embodiment, the imaging lens assembly receives rays fromthe beam source that are transmitted through the sample and form animage on the image sensor. Alternatively, the imaging lens assembly canreceive rays from the beam source that are reflected off of the sampleto form the image on the image sensor.

In certain embodiments, the imaging microscope further comprises anillumination lens assembly that directs the illumination beam at thesample. The illumination lens assembly adjusts the illumination beam sothat the illumination beam illuminates a two-dimensional illuminatedarea on the sample all at once. Additionally, in such embodiments, theimage sensor includes a two-dimensional array of sensors.

In one embodiment, the beam source is a mid-infrared (“MIR”) beam sourceand the illumination beam is at a beam wavelength that is within the MIRrange. In this embodiment, the illumination lens assembly is refractivein the MIR range.

Additionally, in some embodiments, the illumination lens assemblydirects the illumination beam at the sample without splitting andrecombining the illumination beam.

Further, in one embodiment, the illumination lens assembly magnifies theillumination beam. Moreover, the illumination lens assembly can adjustthe size of the illumination beam so that the illuminated area on thesample is at least approximately two hundred and fifty microns by twohundred and fifty microns.

In one embodiment, the imaging lens assembly includes a refractive lensthat directs the rays received by the imaging lens assembly.

Additionally, in some embodiments, the imaging lens assembly receivesthe rays from a plurality of points on the sample and forms the image onthe image sensor without splitting and recombining the received rays.

The present invention is further directed toward a method for generatingan image of a sample, the method comprising the steps of emitting atemporally coherent illumination beam with a beam source, theillumination beam including a plurality of rays; directing the pluralityof rays at the sample; converting an optical image into an array ofelectronic signals with an image sensor; receiving rays from the beamsource that are transmitted through the sample with an imaging lensassembly; and forming an image on the image sensor with the raysreceived from the beam source by the imaging lens assembly that aretransmitted through the sample.

Additionally and/or alternatively, the method can further comprise thesteps of receiving rays from the beam source that are reflected off ofthe sample with the imaging lens assembly; and forming a second image onthe image sensor with the rays received from the beam source by theimaging lens assembly that are reflected off of the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1A is simplified schematic illustration of a sample and anembodiment of an imaging microscope having features of the presentinvention;

FIG. 1B is a simplified schematic illustration of the sample illustratedin FIG. 1A, including a transmission illuminated area;

FIG. 1C is a simplified schematic illustration of the sample illustratedin FIG. 1A, including a reflection illuminated area;

FIG. 2 is a simplified schematic illustration of the sample and anotherembodiment of an imaging microscope having features of the presentinvention;

FIG. 3 is a simplified schematic illustration of the sample and stillanother embodiment of an imaging microscope having features of thepresent invention; and

FIG. 4 is a simplified flowchart demonstrating the use of an imagingmicroscope having features of the present invention to analyze a sample.

DESCRIPTION

FIG. 1A is simplified schematic illustration of a sample 10 and a firstembodiment of an imaging microscope 12 having features of the presentinvention. In particular, the imaging microscope 12 can be used toanalyze and evaluate the various properties of the sample 10. Forexample, in one embodiment, the imaging microscope 12 is an infraredimaging microscope that uses tunable laser radiation tospectroscopically interrogate one or more samples 10 in order to analyzeand identify the properties of the sample.

As an overview, the imaging microscope 12 is uniquely designed toinhibit potential complications from temporal and/or spatial coherencethat may otherwise be present due to the use of laser radiation forimage illumination. Moreover, the present invention provides suchbenefits without the potential drawbacks of complexity of manufactureand operation, increased size and time requirements, increased powerconsumption, high cost, and inefficiency.

The sample 10 can be a variety of things, including human tissue, animaltissue, plant matter, explosive residues, powders, liquids, solids,inks, and other materials commonly analyzed using Fourier transforminfrared (FTIR) microscopes. More particularly, in certain non-exclusiveapplications, the sample 10 can be human tissue and the imagingmicroscope 12 can be utilized for rapid screening of the tissue sample10 for the presence of cancerous cells and/or other health relatedconditions; and/or the imaging microscope 12 can be utilized in certainforensic applications such as rapid screening of the sample 10 for thepresence of explosive residues and/or other dangerous substances.Additionally, when positioned substantially within the imagingmicroscope 12 for purposes of analysis, the sample 10 can be present byitself, or the sample 10 can be held in place using one or more slides,e.g., infrared transparent slides.

Further, the sample 10 can be thin enough to allow study throughtransmission of an illumination beam, e.g., an infrared illuminationbeam, through the sample 10 (i.e. in transmission mode), or the sample10 can be an optically opaque sample that is analyzed through reflectionof an illumination beam, e.g., an infrared illumination beam, by thesample (i.e. in reflection mode). For example, in the embodimentillustrated in FIG. 1A, the imaging microscope 12 can alternatively beutilized in both transmission mode and reflection mode.

In another embodiment, the imaging microscope 12 can be used in bothtransmission mode and reflection mode at the same time. For example,some samples 10 are transmissive to certain wavelengths and reflectiveto other wavelengths. As a more specific, non-exclusive example, lightin the visible spectrum can be directed at the sample 10 for use in thetransmission mode, and MIR light can be directed at the sample 10 foruse in the reflection mode. Still alternatively, the imaging microscope12 can be designed such that it only operates in one of transmissionmode or reflection mode.

The design of the imaging microscope 12 can be varied. In the embodimentillustrated in FIG. 1A, the imaging microscope 12 includes a rigid frame13, a temporally coherent beam source 14, a stage assembly 15 thatretains the sample 10, an imaging lens assembly 16 (e.g., one or morelenses), and an image sensor 18 that converts an optical image into anarray of electronic signals. The design of each of these components canbe varied pursuant to the teachings provided herein.

In one embodiment, the beam source 14 (i) emits a temporally coherent,first illumination beam 20 that is usable for illuminating and analyzingthe sample 10 in transmission mode; and/or (ii) emits a temporallycoherent, second illumination beam 22 that is usable for illuminatingand analyzing the sample 10 in reflection mode. The first illuminationbeam 20 is made up of a plurality of illumination rays 20I that aredirected at the sample 10, and the second illumination beam 22 is madeup of a plurality of illumination rays 22I that are directed at thesample 10. Each illumination beam 20, 22 can be emitted from the samebeam source 14. Alternatively, each illumination beam 20, 22 can beemitted from a separate and distinct beam source. It should be notedthat the use of the terms “first illumination beam” and “secondillumination beam” is merely for ease of description, and eitherillumination beam 20, 22 can be referred to as the “first illuminationbeam” or the “second illumination beam”.

In certain embodiments, the beam source 14 can include (i) a first lasersource 14A that emits the first illumination beam 20, e.g., a firstlaser beam, and (ii) a second laser source 14B that emits the secondillumination beam 22, e.g., a second laser beam. Alternatively, forexample, the beam source 14 can be designed to include a single lasersource with the appropriate beam directors.

Further, in one, non-exclusive embodiment, the beam source 14 isdesigned to provide illumination beams 20, 22 that are in the midinfrared (“MIR”) range spectrum. More particularly, in some suchembodiments, one or both of the laser sources 14A, 14B can be amid-infrared (MIR) beam source that emits the first illumination beam 20and/or the second illumination beam 22 that is at a beam wavelength thatis within the MIR range. For example, one or both of the laser sources14A, 14B can be any type of laser that is capable of generatingradiation in the spectral region of between approximately two to twentymicrons (2-20 μm). Moreover, in alternative embodiments, the lasersources 14A, 14B can be a pulsed laser and/or a continuous wave (CW)laser.

As provided herein, one or both of the laser sources 14A, 14B can be anexternal cavity laser that includes a laser frame 14C, a gain medium14D, a cavity optical assembly 14E, an output optical assembly 14F, anda wavelength dependent (“WD”) feedback assembly 14G.

The laser frame 14C provides a rigid support for the components of eachlaser source 14A, 14B. In one embodiment, the laser frame 14C for eachlaser source 14A, 14B is a single mechanical ground plane that providesstructural integrity for the respective laser source 14A, 14B. Incertain embodiments, the laser frame 14C is made of rigid material thathas a relatively high thermal conductivity.

The design of the gain medium 14D can be varied pursuant to theteachings provided herein. In one, non-exclusive embodiment, the gainmedium 14D for each laser directly emits the respective beams 20, 22without any frequency conversion. As non-exclusive examples, one or bothof the gain mediums 14D can be a Quantum Cascade (QC) gain medium, anInterband Cascade (IC) gain medium, or a mid-infrared diode.Alternatively, another type of gain medium 14D can be utilized.

In FIG. 1A, each gain medium 14D includes (i) a first facet that facesthe respective cavity optical assembly 14E and the feedback assembly14G, and (ii) a second facet that faces the output optical assembly 14F.In this embodiment, each gain medium 14D emits from both facets. In oneembodiment, each first facet is coated with an anti-reflection (“AR”)coating, and each second facet is coated with a reflective coating. TheAR coating allows light directed from the gain medium 14D at the firstfacet to easily exit as a beam directed at the feedback assembly 14G;and allows the light beam reflected from the feedback assembly 14G toeasily enter the gain medium 14D. The beams 20, 22 exit from therespective second facet. The partly reflective coating on the secondfacet of each gain medium 14D reflects at least some of the light thatis directed at the second facet of each gain medium 14D back into therespective gain medium 14D. In one non-exclusive embodiment, the ARcoating can have a reflectivity of less than approximately 2 percent,and the reflective coating can have a reflectivity of betweenapproximately 2-95 percent.

In one embodiment, for each laser source 14A, 14B, (i) the reflectivecoating on the second facet of the gain medium 14D acts as a first end(output coupler) of an external cavity and the feedback assembly 14G(spaced apart from the gain medium 14D) defines a second end of the eachexternal cavity. The term external cavity is utilized to designate thatthe WD feedback assembly 14G is positioned outside of the gain medium14D.

The cavity optical assembly 14E is positioned between the gain medium14D and the feedback assembly 14G along a lasing axis. The cavityoptical assembly 14E collimates and focuses the beam that passes betweenthese components. For example, each cavity optical assembly 14E caninclude one or more lens. For example, the lens can be an asphericallens having an optical axis that is aligned with the respective lasingaxis.

The output optical assembly 14F is positioned between the gain medium14D and the beam redirector assembly 28 in line with the lasing axis tocollimate and focus the beam 22 that exits the second facet of the gainmedium 14D. For example, each output optical assembly 14F can includeone or more lens that are somewhat similar in design to the lens of thecavity optical assemblies 14E.

The WD feedback assembly 14G reflects the beam back to the gain medium14D, and is used to precisely select and adjust the lasing frequency ofthe external cavity and the wavelength of the pulses of light. Stated inanother fashion, the WD feedback assembly 14G is used to feed back tothe gain medium 14D a relatively narrow band wavelength which is thenamplified in the respective gain medium 14D. In this manner, therespective beams 20, 22 may be tuned with the WD feedback assembly 14Gwithout adjusting the respective gain medium 14D. Thus, with theexternal cavity arrangements disclosed herein, the WD feedback assembly14G dictates what wavelength will experience the most gain and thusdominate the wavelength of the beams 20, 22.

In one embodiment, the WD feedback assembly 14G includes a diffractiongrating 14H and a grating mover 141 that selectively moves (e.g.rotates) the grating 14H to adjust the lasing frequency of the gainmedium 14D and the wavelength of the respective beams 20, 22. Thegrating 14H can be continuously monitored with an encoder that providesfor closed loop control of the grating mover 141. With this design, thewavelength of the respective beam 20, 22 can be selectively adjusted ina closed loop fashion so that the sample 10 can be imaged at manydifferent, precise, selectively adjustable wavelengths throughout aportion or the entire MIR spectrum.

Once the beam source 14 has emitted the first illumination beam 20and/or the second illumination beam 22, the illumination beam 20, 22 isdirected toward the sample 10 so that the sample 10 may be properly andeffectively illuminated by the illumination beam 20, 22. For example,when the imaging microscope 12 is operating in transmission mode, thefirst illumination beam 20 (including the plurality of illumination rays20I) is directed toward the sample 10 in order to properly andeffectively illuminate the sample 10. In this example, the rays that aretransmitted through the sample 10 are referred to as transmitted rays20T. In another example, when the imaging microscope 12 is operating inreflection mode, the second illumination beam 22 (including a pluralityof illumination rays 22I) is directed toward the sample 10 in order toproperly and effectively illuminate the sample 10. In this example, therays that are reflected off of the sample 10 are referred to asreflected rays 22R.

In the embodiment illustrated in FIG. 1A, when operating in transmissionmode, the first illumination beam 20 exiting the beam source 14 isdirected with a transmission illumination lens assembly 24 toward andimpinging on the sample 10. In one embodiment, the transmissionillumination lens assembly 24 can include one or more refractive lenses24A (only one is illustrated in phantom) that direct the firstillumination beam 20 at the sample 10. Moreover, the transmissionillumination lens assembly 24 can be refractive in the MIR range.

In certain embodiments, the transmission illumination lens assembly 24adjusts the first illumination beam 20 so that the first illuminationbeam 20 at least illuminates a transmission illuminated area 10A(illustrated in FIG. 1B) on the sample 10 all at once that istwo-dimensional 10. Stated in another fashion, the transmissionillumination lens assembly 24 adjusts the first illumination beam 20 sothat the first illumination beam 20 at least illuminates atwo-dimensional transmission illuminated area 10A simultaneously on thesample 10. With this design, the entire sample 10 or a large portion ofthe sample 10 is simultaneously illuminated and can be examined at thesame time. This expedites the analysis of the sample 10.

In certain embodiments, the transmission illumination lens assembly 24can be used to transform, i.e. to increase (magnify) or decrease, thesize of the first illumination beam 20 to match and simultaneouslyilluminate a desired transmission illuminated area 10A on the sample 10.Stated another way, the transmission illumination lens assembly 24 canbe used to condition and focus the first illumination beam 20 so thatthe first illumination beam 20 has the correct or desired size and beamprofile on the sample 10. In certain embodiments, size of thetransmission illuminated area 10A of the sample 10 is tailored tocorrespond to the design of the image sensor 18 and the imaging lensassembly 16.

FIG. 1B is a simplified schematic illustration of the sample 10illustrated in FIG. 1A, including the transmission illuminated area 10A(illustrated with a box in phantom) that is simultaneously illuminated.In certain embodiments, the two-dimensional transmission illuminationarea 10A is rectangular shaped. More particularly, in some suchembodiments, the two-dimensional transmission illumination area 10A canbe square shaped. For example, in alternative non-exclusive embodiments,the transmission illumination lens assembly 24 can adjust the size ofthe first illumination beam 20 so that the transmission illuminated area10A that is simultaneously illuminated on the sample 10 is at leastapproximately (i) two hundred and fifty microns (250 μm) by two hundredand fifty microns (250 μm); (ii) five hundred microns (500 μm) by fivehundred microns (500 μm); (iii) seven hundred and fifty microns (750 μm)by seven hundred and fifty microns (750 μm); (iv) one millimeter (1 mm)by one millimeter (1 mm); (v) one and a half millimeter (1.5 mm) by oneand a half millimeter (1.5 mm); and (vi) two millimeters (2 mm) by twomillimeters (2 mm); or (vii) three millimeters (3 mm) by threemillimeters (3 mm). Still alternatively, the transmission illuminatedarea 10A can have a non-square shape. As non-exclusive examples, thetransmission illumination lens assembly 24 can adjust the size of thefirst illumination beam 20 so that the transmission illuminated area 10Aon the sample 10 is at least approximately two hundred microns (200 μm)by three hundred microns (300 μm); or (iii) fifty microns (50 μm) byfive hundred microns (500 μm). Alternatively, the transmissionillumination lens assembly 24 can adjust the size of the firstillumination beam 20 so that the transmission illuminated area 10A onthe sample 10 has a different size or shape than the examples providedabove. For example, in alternative, non-exclusive embodiments, thetransmission illumination lens assembly 24 can adjust the size of thefirst illumination beam 20 so that the transmission illuminated area 10Ais at least approximately 20, 30, 30, 50, 60, 70, 80, 90, or 100millimeters squared. Still alternatively, for example, thetwo-dimensional transmission illuminated area 10A can be circular oroval shaped.

Further, as shown in FIG. 1B, the transmission illuminated area 10A isreally an effectively illuminated area (has substantially uniformintensity) that exists within a larger, fully illuminated area 10B thatis simultaneously illuminated by the first illumination beam 20(illustrated in FIG. 1A). As illustrated, the fully illuminated area 10Bcan be substantially circular shaped and can be the result of the firstillumination beam 20 having a substantially circular shapedcross-section. Alternatively, the first illumination beam 20, and thusthe fully illuminated area 10B can have another shape.

Moreover, referring back to FIG. 1A, the transmission illumination lensassembly 24 transforms the size and profile of the first illuminationbeam 20 as desired without splitting the illumination rays 20I of thefirst illumination beam 20 into multiple paths that, if recombined, cancause interference at the sample 10. Stated another way, thetransmission illumination lens assembly 24 directs the firstillumination beam 20 at the sample 10 without splitting and recombiningthe illumination rays 20I of the first illumination beam 20.

Alternatively, in another embodiment, if the first illumination beam 20has sufficient extent to allow illumination of the desired area size ofthe sample 10, then the imaging microscope 12 can be designed withoutthe transmission illumination lens assembly 24, and the firstillumination beam 20 can be directly shined onto the sample 10.

In the embodiment illustrated in FIG. 1A, the imaging microscope 12 alsocan include a reflection illumination lens assembly 26 for directing thesecond illumination beam 22 at the sample 10 when operating inreflection mode. In one embodiment, the reflection illumination lensassembly 26 includes one or more lenses 26A, a redirector 28, e.g., amirror, and a transmitter-redirector 30, e.g., a beam splitter. In thisembodiment, one or more of the lenses 26A of the reflection illuminationlens assembly 26 can be refractive in the MIR range. In thenon-exclusive embodiment illustrated in FIG. 1A, the lens assembly 26includes two, spaced apart lenses 26A.

Additionally, in certain embodiments, the reflection illumination lensassembly 26 adjusts the second illumination beam 22 so that the secondillumination beam 22 at least illuminates a reflection illuminated area100 (illustrated in FIG. 10) on the sample 10 all at once that istwo-dimensional. Stated in another fashion, the reflection illuminationlens assembly 26 adjusts the second illumination beam 22 so that thesecond illumination beam 22 illuminates a two-dimensional reflectionilluminated area 100 simultaneously on the sample 10. With this design,the entire sample 10 or a large portion of the sample 10 issimultaneously illuminated and can be examined at the same time. Thisexpedites the analysis of the sample 10. In certain embodiments, thereflection illumination lens assembly 26 conditions the secondillumination beam 22 to allow for the broad illumination of thereflection illuminated area 100 through a first lens 32 of the imaginglens assembly 16. In this embodiment, the same first lens 32 is useddirect the second illumination beam 22 at the sample 10 and is used asthe objective for the beams reflected off the sample 10.

In certain embodiments, the reflection illumination lens assembly 26 canbe used to transform, i.e. to increase (magnify) or decrease, the sizeof the second illumination beam 22 to match a desired reflectionilluminated area 100 on the sample 10. Stated another way, thereflection illumination lens assembly 26 can be used to condition andfocus the second illumination beam 22 so that the second illuminationbeam 22 has the desired beam profile on the sample 10.

FIG. 10 is a simplified schematic illustration of the sample 10including the reflection illuminated area 100. In certain embodiments,the two-dimensional reflection illumination area 100 is rectangularshaped. More particularly, in some such embodiments, the two-dimensionalreflection illumination area 100 can be square shaped. For example, inalternative, non-exclusive embodiments, the reflection illumination lensassembly 26 can adjust the size of the second illumination beam 22 sothat the reflection illuminated area 100 on the sample 10 is at leastapproximately (i) two hundred and fifty microns (250 μm) by two hundredand fifty microns (250 μm); (ii) five hundred microns (500 μm) by fivehundred microns (500 μm); (iii) seven hundred and fifty microns (750 μm)by seven hundred and fifty microns (750 μm); (iv) one millimeter (1 mm)by one millimeter (1 mm); (v) one and a half millimeter (1.5 mm) by oneand a half millimeter (1.5 mm); and (vi) two millimeters (2 mm) by twomillimeters (2 mm); or (vii) three millimeters (3 mm) by threemillimeters (3 mm). Still alternatively, the reflection illuminated area100 can have a non-square shape. As non-exclusive examples, thetransmission illumination lens assembly 24 can adjust the size of thefirst illumination beam 20 so that the transmission illuminated area 10Aon the sample 10 is at least approximately two hundred microns (200 μm)by three hundred microns (300 μm); or (iii) fifty microns (50 μm) byfive hundred microns (500 μm). Alternatively, the reflectionillumination lens assembly 26 can adjust the size of the secondillumination beam 22 so that the reflection illuminated area 100 on thesample 10 has a different size or shape than the examples providedabove. For example, in alternative, non-exclusive embodiments, thereflection illumination lens assembly 26 can adjust the size of thesecond illumination beam 22 so that the reflection illuminated area 100is at least approximately 20, 30, 30, 50, 60, 70, 80, 90, or 100millimeters squared. Still alternatively, for example, thetwo-dimensional reflection illuminated area 100 can be circular or ovalshaped.

Further, as shown in FIG. 10, the reflection illuminated area 100 can bean effectively illuminated area (has substantially uniform intensity)that exists within a larger, fully illuminated area 10D that isilluminated by the second illumination beam 22 (illustrated in FIG. 1A).As illustrated, the fully illuminated area 10D can be substantiallycircular shaped and can be the result of the second illumination beam 22having a substantially circular shaped cross-section. Alternatively, thesecond illumination beam 22, and thus the fully illuminated area 100 canhave another shape.

Referring back to FIG. 1A, in certain embodiments, the reflectionillumination lens assembly 26 transforms the size and profile of thesecond illumination beam 22 as desired without splitting and recombiningthe illumination rays 22I into multiple paths that, if recombined, cancause interference at the sample 10. Stated another way, the reflectionillumination lens assembly 26 directs the illumination rays 22I of thesecond illumination beam 22 at the sample 10 without splitting andrecombining the illumination rays 22I.

Additionally, in alternative embodiments, the reflection illuminationlens assembly 26 can be positioned such that the second illuminationbeam 22 passes through the reflection illumination lens assembly 26before and/or after the second illumination beam 22 is redirected by theredirector 28.

The redirector 28 is utilized to initially redirect the secondillumination beam 22 so that the second illumination beam 22 can beproperly directed toward a side (e.g. the bottom or the top depending onthe design) of the sample 10 that will reflect the second illuminationbeam 22 toward the imaging lens assembly 16. The design of theredirector 28 can be varied. In one embodiment, the redirector 28 can bea mirror (reflective in the desired wavelength spectrum) which ispositioned so as to redirect the path of the second illumination beam 22by approximately ninety degrees. Alternatively, the redirector 28 canhave a different design and/or the redirector 28 can be positioned so asto redirect the path of the second illumination beam 22 by greater thanor less than approximately ninety degrees. Still alternatively, theredirector 28 can include a curved mirror that conditions the secondillumination beam 22 (i) to complement the reflection illumination lensassembly 26, or (ii) to allow for the elimination of a portion or all ofthe reflection illumination lens assembly 26.

Moreover, in reflection mode, in FIG. 1A, the second illumination beam22 is directed at the sample 10 with the transmitter-redirector 30 toavoid multiple beam paths, and to decrease the number of paths thereflected or scattered second illumination beam 22 can take whentraveling from the sample 10 to the image sensor 18. The design of thetransmitter-redirector 30 can be varied to suit the specificrequirements of the imaging microscope 12. In certain embodiments, thetransmitter-redirector 30 can be a beam splitter, e.g., a fifty percent(50%) beam splitter, which redirects a first portion 22F of theillumination rays 22I of the second illumination beam 22 toward thesample 10, and transmits a second portion (not shown) of theillumination rays 22I of the second illumination beam 22. The secondportion of the second illumination beam 22 is subsequently directed awayfrom the system and not used by the imaging microscope 12. It should benoted that the second (or discarded) portion of the second illuminationbeam 22 that is generated from this first pass through thetransmitter-redirector 30 is not shown in FIG. 1A for purposes ofclarity.

With the second illumination beam 22 being redirected by thetransmitter-redirector 30 before impinging on the sample 10, as providedabove, the reflection illumination lens assembly 26 can be used totransform the second illumination beam 22 so that it providesillumination for the two-dimensional reflection illuminated area 10Cacross the sample 10, instead of being focused to a point by the firstlens 32 of the imaging lens assembly 16. In certain embodiments, thetransmitter-redirector 30 can be made from a variety of infraredtransmissive materials, such as ZnSe or Ge, or other materials.Additionally, the transmitter-redirector 30 can be a plano-plano beamsplitter, with one side anti-reflection (AR) coated, and the othercoated or uncoated for partial reflectivity. The transmitter-redirector30 can also provide lensing action for transforming the secondillumination beam 22 as desired. The transmitter-redirector 30 can alsoincorporate design elements to eliminate first and second surfaceinterference effects due to the coherent nature of the illumination beam22. As non-exclusive examples, design elements that would reduce thesurface interference effects include anti-reflective coatings (for thewavelength of the beam), wedged elements, and/or curved opticalsurfaces.

The stage assembly 15 retains the sample 10, and can be used to properlyposition the sample 10. For example, the stage assembly 15 can include astage 15A that retains sample 10, and stage mover 15B that selectivelymoves the stage 15A and the sample 10. For example, the stage mover 15Bcan include one or more actuators, or stage 15A can be manuallypositioned.

When the illumination rays 20I of the first illumination beam 20 areilluminating the sample 10, at least a portion of the transmitted rays20T that are transmitted through the sample 10 are received by theimaging lens assembly 16 and imaged on the image sensor 18. Somewhatsimilarly, when the illumination rays 22I of the second illuminationbeam 22 are illuminating the sample 10, at least a portion of thereflected rays 22R that are reflected from the sample 10 are received bythe imaging lens assembly 16 and imaged on the image sensor 18. Statedin another fashion, the imaging lens assembly 16 receives at least aportion of the transmitted rays 20T that are transmitted through thesample 10, or at least a portion of the reflected rays 22R that arereflected from the sample 10 and forms an image on the image sensor 18.

As utilized herein, the term “imaged rays” 18A shall mean thetransmitted rays 20T or the reflected rays 22R that are collected by theimaging lens assembly 16 and imaged on the image sensor 18. As providedherein, the imaging lens assembly 16 receives the imaged rays 18A from aplurality of points on the sample 10 and forms the image on the imagesensor 18 without splitting and recombining the imaged rays 18A. Thisreduces interference effects at the image sensor 18.

In one embodiment, the imaging lens assembly 16 can include a first lens32 and a second lens 34 that cooperate to form an image of the sample 10on the image sensor 18. Alternatively, the imaging lens assembly 16 caninclude greater than two lenses or only one lens.

In one embodiment, the first lens 32 can be an objective lens thatcollects the imaged rays 18A, and focuses the imaged rays 18A on theimage sensor 18. Moreover, as illustrated, the first lens 32 ispositioned substantially between the sample 10 and the second lens 34.Additionally, in one embodiment, the second lens 34 can be a projectionlens that projects the imaged rays 18A toward the image sensor 18.Moreover, as illustrated, the second lens 34 is positioned substantiallybetween the first lens 32 and the image sensor 18. Further, in oneembodiment, one or both of the lenses 32, 34 can be refractive in theMIR range or the wavelength of the illumination beam. Still further, oneor both of the lenses 32, 34 can be a compound lens.

Each of the lenses 32, 34 can be types such as plano-convex,plano-concave, miniscus, and aspherical, as well as other types. Forrefractive lenses, materials such as ZnSe, Ge, chalcogenide glass, andother materials can be employed. Reflective lenses can be elliptical,paraboloid, or other shapes. The reflective surface can be dichroiccoating, Au, Ag, or other surface types. In one non-exclusiveembodiment, the first lens 32, i.e. the objective lens, can be a 10millimeter diameter, 10 millimeter focal length, plano-aspheric Ge lens,and the second lens 34, i.e. the projection lens, can be a 20 millimeterdiameter, 50 millimeter focal length plano-convex Ge lens. This providesa magnification of 5× at the image sensor 18, allowing an imageresolution of 3.4 μm for a 17 μm pitch pixel. It should be noted thatthe resolution of the image sensor 18 is described in more detail below.Alternatively, other lenses are possible that allow differentmagnifications. Single and compound lenses that are designed to beachromats over the desired infrared spectral region can also be used.

Further, as shown in the embodiment illustrated in FIG. 1A, thetransmitted rays 20T or the reflected rays 22R that are collected by thefirst lens 32 are directed at the transmitter-redirector 30 that ispositioned between the first lens 32 and the second lens 34 in thisexample. In this embodiment, if the transmitter-redirector 30 is a fiftypercent (50%) beam splitter, the transmitted rays 20T or the reflectedrays 22R that are collected by the first lens 32 are split into (i) theimaged rays 18A that are imaged on the image sensor 18, and (ii)discarded rays that are directed away from the image sensor 18.

The image sensor 18 senses the imaged rays 18A and converts the imagedrays 18A (the optical image) into an array of electronic signals thatrepresents an image of the sample.

In certain embodiments, the image sensor 18 includes a two dimensionalarray of photosensitive elements (pixels) (e.g. a focal plane array(FPA)) that are sensitive to the wavelength of the illumination beams20I, 22I that are used to construct a two-dimensional image. The spacingbetween the pixel elements is referred to as the pitch of the array. Forexample, if the illumination beams 20I, 22I are in the MIR range, theimage sensor 18 is a MIR imager. More specifically, if the illuminationbeams 20I, 22I are in the infrared spectral region from two to twentyμm, the image sensor 18 is sensitive to the infrared spectral regionfrom two to twenty μm.

Examples of suitable infrared image sensors 18 include (i) vanadiumoxide (VO_(x)) microbolometer arrays such as the FPA in the FLIR Tau 640infrared camera that are typically responsive in the seven to fourteenμm spectral range; (ii) mercury cadmium telluride (HgCdTe or MCT) arrayssuch as those in the FLIR Orion SC7000 Series cameras that areresponsive in the 7.7 to 11.5 μm spectral range; (iii) indium antimonide(InSb) arrays such as those in the FLIR Orion SC7000 Series cameras thatare responsive in the 1.5 to 5.5 μm spectral range; (iv) indium galliumarsenide (InGaAs); (v) uncooled hybrid arrays involving VOx and othermaterials from DRS that are responsive in the two to twenty μm spectralrange; or (vi) any other type of image sensor 18 that is designed to besensitive to infrared light in the two to twenty μm range and haselectronics allowing reading out of each element's signal level togenerate a two-dimensional array of image information.

In alternative, non-exclusive embodiments, the pixel dimensions for theimage sensor 18 can be five, eight, ten, twelve, thirteen, seventeen,twenty-five, thirty-five, and fifty μm per side, for example.Additionally, the pixels can be square, rectangular, or any other shape.As non-exclusive examples, the image sensor 18 can be designed toinclude a 50×50 array of pixels; a 100×100 array of pixels, a 200×200array of pixels, a 320×240 array of pixels, a 400×400 array of pixels, a500×500 array of pixels, a 640×480 array of pixels, or another sizedarray of pixels. Further, the arrays can be square or rectangular, ormasked for a specific shape, either physically or through dataprocessing.

In one non-exclusive example, the image sensor 18 can be amicrobolometer array having a pixel pitch of 17 μm and a frame size of640×512, resulting in a physical FPA size of 10.88 mm×8.7 mm. With fivetimes magnification for the first lens 32, i.e. the objective lens, andthe second lens 34, i.e. the projection lens, this results in an areaimaged at the sample 10 of 2.2 mm×1.7 mm. Therefore, the size of theillumination beam 20, 22 should be sufficient to provide illuminationacross this area on the sample 10. If the 95% beam diameter is at leastthree millimeters, the illumination beam 20, 22 can provide appropriateillumination across the sample 10 as necessary.

In certain embodiments, the present invention allows the use of lowerpriced, room temperature image sensors 18, e.g., FPAs such asmicrobolometers. These FPAs require lower power consumption and havesmaller overall volume, such that field-deployable and commercialinstruments become more practical. Additionally, the use of tunableinfrared lasers, such as QC lasers 14A, 14B, generates enough light toallow the use of these less-sensitive room temperature FPAs. Inparticular, the use of such an FPA allows for a complete image to becaptured at each wavelength. Moreover, due to the higher power providedby such lasers 14A, 14B, less signal averaging is thus required, meaningthat it is possible to rapidly tune the laser 14A, 14B and then build upa spectral image cube for analysis in tens of seconds, rather than theminutes generally required for FTIR microscopes.

As a non-exclusive example, tunable infrared lasers, such as QC lasers14A, 14B, can generate between approximately 0.2 mW to 20 mW at a singlewavelength. This will provide enough intensity to overcome thebackground pixel noise level of less-sensitive microbolometer arrays.

As provided herein, in certain embodiments, the imaging device 12 isdesigned so that (i) the illumination rays 20I generated by the firstlaser source 14A are directed at the sample 10 without splitting andrecombining the illumination rays 20I, e.g. illumination rays 20I followa single path to the sample 10; (ii) the illumination rays 22I generatedby the second laser source 14B are directed at the sample 10 withoutsplitting and recombining the illumination rays 22I, e.g. theillumination rays 22I follow a single path to the sample 10; and (iii)the imaged rays 18A travel from the sample 10 to the image sensor 18without splitting and recombining the imaged rays 18A, e.g. the imagedrays 18A follow a predominantly single path to the image sensor 18. Withthis design, potential drawbacks from the use of a temporally coherentlight source, such as certain interference effects, e.g., interferencefringes, can be avoided. Spatial coherence occurs when the variation inthe electric field wavefront of the light is similar across anilluminated area. The effects on imaging of spatial coherence includespeckle and diffraction. Temporal coherence means that the electricfield of the light exhibits the same oscillation pattern over asignificant period of time, such as a sinusoidal oscillation. Whereasspatial coherence can occur even for waves that do not have a regular,sinusoidal electric field, temporal coherence requires a periodic,regular oscillation in the electric field. This presents a particularchallenge for imaging because laser light originating from a singlesource, which is subsequently split such that portions of the laserlight travel different paths, and which is then recombined, can exhibitinterference effects. For example, the effects of temporal coherence canbe seen in terms of interference fringes. More particularly, lightemanating from an illuminating laser that is split and allowed to traveltwo separate paths before being rejoined at a sample, can result ininterference fringes being evident on an illuminated sample. As detailedherein, the present design effectively enables such potential drawbacksto be avoided.

Additionally, as illustrated in FIG. 1A, the imaging microscope 12 canfurther include and/or be coupled to a processing device 36 thatincludes one or more processors and/or storage devices. For example, theprocessing device 36 can receive information from the pixels of theimage sensor 18 and generate the image of the sample. Further, theprocessing device 36 can control the operation of the laser sources 14A,14B and the stage assembly 15.

FIG. 2 is a simplified schematic illustration of the sample 10 andanother embodiment of an imaging microscope 212 having features of thepresent invention. The imaging microscope 212 illustrated in FIG. 2 issomewhat similar to the imaging microscope 12 illustrated and describedabove in relation to FIG. 1A. For example, the imaging microscope 212includes a temporally coherent beam source 214 that includes a lasersource 214A, a stage assembly 215, an imaging lens assembly 216, animage sensor 218, and a processing device 236 that are somewhat similarto the corresponding components illustrated and described above inrelation to FIG. 1A. However, in the embodiment illustrated in FIG. 2,the imaging microscope 212 is designed to only function in thetransmission mode with an in line format, and the imaging microscope 212does not function in the reflection mode.

In this embodiment, because the imaging microscope 212 is only designedto function in transmission mode, the imaging microscope 212 can bedesigned without the illumination optics that are included in theembodiment illustrated in FIG. 1A to enable the imaging microscope 12 toalternatively function in reflection mode. Accordingly, in thisembodiment, the imaging microscope 212 does not include the reflectionillumination lens assembly 26, the redirector 28 and thetransmitter-redirector 30 that are at least optionally included in theembodiment illustrated in FIG. 1A.

Similar to the previous embodiment, the temporally coherent beam source214 emits a temporally coherent illumination beam 220 that includes aplurality of illumination rays 220I for illuminating and analyzing thesample 10 in transmission mode.

The transmission illumination lens assembly 224 can again adjust theillumination beam 220 so that the illumination beam 220 illuminates atwo dimensional transmission illuminated area, e.g., the transmissionilluminated area 10A illustrated in FIG. 1B, on the sample 10 all atonce.

Subsequently, at least some of the transmitted rays 220T that aretransmitted through the sample 10 are then directed toward the imagesensor 218 with the imaging lens assembly 216. The transmitted rays 220Tcollected by the imaging lens assembly 216 and directed at the imagesensor 218 are referred to as imaged rays 218A. As with the previousembodiment, the imaging lens assembly 216 can include a first lens 232and a second lens 234 that cooperate to form an image of the sample 10on the image sensor 218. Alternatively, the imaging lens assembly 216can include greater than two lenses or only one lens.

FIG. 3 is a simplified schematic illustration of the sample 10 and stillanother embodiment of an imaging microscope 312 having features of thepresent invention. The imaging microscope 312 illustrated in FIG. 3 issomewhat similar to the imaging microscope 12 illustrated and describedabove in relation to FIG. 1A. For example, the imaging microscope 312includes a temporally coherent beam source 314 with a laser source 314B,a stage assembly 315, an imaging lens assembly 316, an image sensor 318,and a processing device 336 that are somewhat similar to correspondingcomponents illustrated and described above in relation to FIG. 1A.However, in the embodiment illustrated in FIG. 3, the imaging microscope312 is designed to only function in the reflection mode, and the imagingmicroscope 312 does not function in the transmission mode. Moreparticularly, because the imaging microscope 312 is only designed tofunction in reflection mode, the imaging microscope 312 can be designedwithout the transmission illumination lens assembly 24 that is at leastoptionally included in the embodiment illustrated in FIG. 1A.

Similar to the previous embodiment, the temporally coherent beam source314 emits a temporally coherent illumination beam 322 that includes aplurality of illumination rays 322I for illuminating and analyzing thesample 10 in reflection mode.

The reflection illumination lens assembly 326 can again adjust theillumination beam 322 so that the illumination beam 322 illuminates atwo dimensional reflection illuminated area, e.g., the reflectionilluminated area 100 illustrated in FIG. 10, on the sample 10 all atonce.

Subsequently, at least some of the reflected rays 322R that arereflected from the sample 10 are then directed toward the image sensor318 with the imaging lens assembly 316. The reflected rays 322Rcollected by the imaging lens assembly 316 and directed at the imagesensor 318 are referred to as imaged rays 318A. As with the previousembodiment, the imaging lens assembly 316 can include a first lens 332and a second lens 334 that cooperate to form an image of the sample 10on the image sensor 318. Alternatively, the imaging lens assembly 316can include greater than two lenses or only one lens.

In this embodiment, the reflection illumination lens assembly 326 againincludes one or more lenses 326A (two are illustrated in FIG. 3), aredirector 328, and a transmitter-redirector 330 that are similar to thecorresponding components described above and illustrated in FIG. 1A.

FIG. 4 is a simplified flowchart demonstrating the use of an imagingmicroscope having features of the present invention to analyze a sample.Although it is disclosed that the steps employed in the use of theimaging microscope are performed in a certain order, it should be notedthat the steps can be performed in a different order, and/or one or moreof the steps can be combined or eliminated without altering the overallintended scope and breadth of the present invention.

Initially, in step 401, a sample is obtained that it is desired toanalyze utilizing the imaging microscope. Additionally, in step 403, thesample is visually inspected to determine whether the sample isappropriate for analysis in transmission mode or reflection mode. Inparticular, if the sample is thin and/or substantially transparent, thenthe sample is more appropriate for analysis in the transmission mode.Alternatively, if the sample is substantially opaque such that theillumination beam will likely be reflected by the sample, then thesample is more appropriate for analysis in the reflection mode.

In step 405, the sample is positioned near a temporally coherent beamsource within the imaging microscope for analysis. Further, in step 407,the temporally coherent beam source of the imaging microscope, e.g., alaser source that operates in the infrared spectral region between twoand twenty μm, is tuned to a particular wavelength.

Then, in step 409, the beam source is activated in order to generate afirst image of the sample. As disclosed herein above, the beam sourceilluminates a two-dimensional area of the sample all at once, which isthen imaged onto an image sensor, e.g., an image sensor that isresponsive somewhere in the infrared spectral region from two to twentyμm, through one or more lenses, e.g., an objective lens and a projectionlens. The illumination provided by the beam source is necessarilycontrolled so that a set of single path rays from the illumination beamtraverses a single path before impinging on the sample and between thesample and the image sensor. Stated another way, the illuminationprovided by the beam source is controlled so that the set of single pathrays are not split and recombined between the beam source and thesample, and the set of single path rays are not split and recombinedbetween the sample and the image sensor.

If it has been determined that the imaging microscope should beappropriately utilized in transmission mode for the particular samplebeing analyzed, then the beam source should be activated so as tosubstantially directly illuminate the sample. Alternatively, if it hasbeen determined that the imaging microscope should be appropriatelyutilized in reflection mode for the particular sample being analyzed,then the beam source should be activated so as to illuminate the backside of the sample utilizing the appropriate optical elements. It shouldbe noted that if an insufficient image is generated with the imagingmicroscope in the mode chosen, i.e. either transmission mode orreflection mode, then the alternative mode can be activated to provide amore sufficient and/or appropriate image generated from the sample.

In step 411, the beam source is deactivated, i.e. is turned off, and asecond image of the sample is captured by the image sensor without theuse of the temporally coherent beam source. Then, in step 413, thesecond image of the sample acquired without the beam source issubtracted from the first image of the sample acquired utilizing thebeam source to create a differential image of the sample that consistsentirely of transmitted or reflected light from the beam source.

Subsequently, in step 415, the process of steps 407 through 413 isrepeated as necessary with the beam source tuned to additionalappropriate wavelengths. This creates a set of images at differentwavelengths of the beam source, known as a spectral image cube, orhypercube. Then, in step 417, the spectral image cube can be analyzed ateach pixel or set of pixels to generate a transmission or reflectionspectrum. Next, in step 419, the spectrum can then be analyzed todetermine properties of the sample at different positions across thesample. These properties can be chemical, structural, or phase, forexample. Finally, in step 421, the analyzed data is then used to createa two-dimensional map of sample properties that can be visually overlaidon a picture of the sample to identify regions of the sample withdifferent sample properties.

In summary, as disclosed herein, the present invention allows thecreation of an infrared imaging microscope for spectral analysis thathas many advantages over traditional technology based on FTIRspectrometers. In particular, the present invention is meant to dealwith the difficulties of illumination and imaging with a temporallycoherent illumination beam that originates from a temporally coherentbeam source such as a laser. As disclosed herein, the way to provideuniform, interference fringe free illumination is to eliminate multiplebeam paths from the beam source to the sample 10, and from the sample 10to the image sensor. More specifically, as provided herein, the opticsare designed to allow interference-free illumination of a sample byusing a illumination beam that has been transformed through reflectionsand lens elements alone, and not split into different paths andrecombined. Similarly, the optics train for imaging the sample 10 ontothe image sensor, e.g., onto a focal plane array, is meant to interactwith the largely single transmission or reflection beam path from thelaser illumination, and to map this to the image sensor withoutsplitting into different paths and recombining.

In one embodiment, the imaging microscope can include a illuminationbeam, e.g., an infrared laser beam from a tunable QC laser, which can bedirectly pointed to the sample 10 in transmission mode. In suchembodiment, the illumination beam, e.g., an infrared laser beam, canhave an extent of approximately 3 mm×3 mm, so it illuminates the sample10 nearly uniformly, without visible interference fringes. This directillumination removes multiple beam paths. Without this invention,illumination with such an illumination beam would produce significantinterference effects due to the temporal coherence of the beam source.With the invention, these effects are gone, allowing fast acquisition ofan image with no interference artifacts.

Additionally, in reflection mode, the illumination beam can be coupledin through a transmitter-redirector, e.g., a beam splitter, to providethe same effect. Because the illumination beam traverses an objectivelens before impinging on the sample 10, an illumination lens can beemployed to project the illumination beam onto the sample 10 withsufficient extent to provide sufficient illumination.

Moreover, the present invention allows the use of a compact opticaltrain based on refractive optical components. This in turn lends itselfto a compact instrument design that is easier to manufacture, morerobust for field deployment, and more cost effective for commercialproducts.

While a number of exemplary aspects and embodiments of an imagingmicroscope 12 have been discussed above, those of skill in the art willrecognize certain modifications, permutations, additions andsub-combinations thereof. It is therefore intended that the followingappended claims and claims hereafter introduced are interpreted toinclude all such modifications, permutations, additions andsub-combinations as are within their true spirit and scope.

What is claimed is:
 1. An imaging microscope for analyzing a sample, theimaging microscope comprising: a beam source that emits a temporallycoherent, first illumination beam that is directed at the sample, andsubsequently emits a temporally coherent, second illumination beam thatis directed at the sample, wherein each illumination beam includes aplurality of rays; wherein each illumination beam is in the mid-infraredrange; wherein the beam source includes a mid-infrared tunable laser; animage sensor that includes a two-dimensional array of sensors thatconvert an optical image into an array of electronic signals; and animaging lens assembly that receives the rays from the sample and forms atwo-dimensional, first optical image of the sample on the image sensorwithout splitting and recombining the received rays when the firstillumination beam is directed at the sample; and wherein the imaginglens assembly receives the rays from the sample and forms atwo-dimensional, second optical image of the sample on the image sensorwithout splitting and recombining the received rays when the secondillumination beam is directed at the sample.
 2. The imaging microscopeof claim 1 wherein the first illumination beam has a first wavelength,and the second illumination beam has a second wavelength that isdifferent than the first wavelength.
 3. The imaging microscope of claim1 further comprising an illumination lens assembly that directs theillumination beams at the sample without splitting and recombining theillumination beams, the illumination lens assembly adjusting theillumination beams so that each of the illumination beams illuminates atwo-dimensional illuminated area on the sample.
 4. The imagingmicroscope of claim 1 further comprising (i) an illumination lensassembly that directs the first illumination beam at the sample withoutsplitting and recombining the first illumination beam, the illuminationlens assembly adjusting the first illumination beam so that the firstillumination beam illuminates a two-dimensional illuminated area on thesample; and (ii) a reflection lens assembly that directs the secondillumination beam at the sample without splitting and recombining thesecond illumination beam, the reflection lens assembly adjusting thesecond illumination beam so that the second illumination beamilluminates a two-dimensional illuminated area on the sample.
 5. Theimaging microscope of claim 4 wherein the imaging lens assembly includesan objective lens and a projection lens; and wherein the reflection lensassembly includes a beam splitter positioned between the objective lensand the projection lens, the beam splitter redirecting a portion of thesecond illumination beam at the sample, and the beam splittertransmitting a portion of the rays received by the imaging lensassembly.
 6. The imaging microscope of claim 1 further comprising areflection lens assembly that directs the illumination beams at thesample without splitting and recombining the illumination beams, thereflection lens assembly adjusting the illumination beams so that eachof the illumination beams illuminates a two-dimensional illuminated areaon the sample.
 7. The imaging microscope of claim 6 wherein the imaginglens assembly includes an objective lens and a projection lens; andwherein the reflection lens assembly includes a beam splitter positionedbetween the objective lens and the projection lens, the beam splitterredirecting a first portion of the rays at the sample, and the beamsplitter transmitting a second portion of the rays received by theimaging lens assembly.
 8. The imaging microscope of claim 1 wherein themid-infrared tunable laser includes a quantum cascade gain medium.
 9. Animaging microscope for analyzing a sample, the imaging microscopecomprising: a slide that retains the sample; a stage assembly thatretains the slide and selectively moves the sample; a beam source thatemits (i) a temporally coherent first illumination beam, the firstillumination beam including a plurality of first rays, and (ii) atemporally coherent, second illumination beam, the second illuminationbeam including a plurality of second rays; wherein the beam sourceincludes a mid-infrared tunable laser; an illumination lens assemblythat directs the first illumination beam at the sample retained by theslide, the illumination lens assembly adjusting the first illuminationbeam so that the first illumination beam illuminates a two-dimensionalilluminated area on the sample all at once; a reflection lens assemblythat directs the second illumination beam at the sample retained by theslide, the reflection lens assembly adjusting the second illuminationbeam so that the second illumination beam illuminates a two-dimensionalilluminated area on the sample all at once; an image sensor thatconverts a two dimensional, optical image into an array of electronicsignals, the image sensor including a two-dimensional array of sensorsthat are used to construct a two-dimensional image of the sample; and animaging lens assembly that receives transmitted rays that aretransmitted through the sample when the first illumination beam isdirected at the sample, and forms a two-dimensional, first optical imageof the sample on the image sensor without splitting and recombining thetransmitted rays; and wherein the imaging lens assembly further receivesreflected rays that are reflected off the sample when the secondillumination beam is directed at the sample, and forms atwo-dimensional, second optical image of the sample on the image sensorwithout splitting and recombining the reflected rays.
 10. The imagingmicroscope of claim 9 wherein the first illumination beam has a firstwavelength that is in the mid-infrared range, and the secondillumination beam has a second wavelength that is in the mid-infraredrange, and wherein the second wavelength is different than the firstwavelength.
 11. The imaging microscope of claim 10 wherein themid-infrared tunable laser includes a quantum cascade gain medium. 12.The imaging microscope of claim 9 wherein the imaging lens assemblyincludes an objective lens and a projection lens; and wherein thereflection lens assembly includes a beam splitter positioned between theobjective lens and the projection lens, the beam splitter redirecting aportion of the second rays at the sample, and the beam splittertransmitting a portion of the reflected rays received by the imaginglens assembly.
 13. The imaging microscope of claim 9 wherein theillumination lens assembly directs the first illumination beam at thesample without splitting and recombining the first illumination beam.14. The imaging microscope of claim 13 wherein the reflection lensassembly directs the second illumination beam at the sample withoutsplitting and recombining the second illumination beam.
 15. The imagingmicroscope of claim 9 wherein the reflection lens assembly directs thesecond illumination beam at the sample without splitting and recombiningthe second illumination beam.
 16. The imaging microscope of claim 9wherein the mid-infrared tunable laser includes a quantum cascade gainmedium.
 17. An imaging microscope for generating a two-dimensional imageof a sample, the imaging microscope comprising: a beam source that emitsa temporally coherent first illumination beam, the first illuminationbeam including a plurality of first rays; wherein the beam sourceincludes a mid-infrared tunable laser and the first illumination beamhas a first wavelength that is in the mid-infrared range; anillumination lens assembly that directs the first illumination beam atthe sample, the illumination lens assembly adjusting the firstillumination beam so that the first illumination beam illuminates atwo-dimensional illuminated area on the sample all at once; an imagesensor that converts a two dimensional, optical image into an array ofelectronic signals, the image sensor including a two-dimensional arrayof sensors that are used to construct the two-dimensional image of thesample; and an imaging lens assembly that receives rays from a pluralityof points on the sample and forms a two-dimensional, first optical imageof the sample on the image sensor.
 18. The imaging microscope of claim17 wherein the imaging lens assembly receives the rays from the sampleand forms the two-dimensional, first optical image of the sample on theimage sensor without splitting and recombining the received rays. 19.The imaging microscope of claim 17 wherein the illumination lensassembly adjusts the size of the first illumination beam so that theilluminated area on the sample is at least approximately twentymillimeters squared.
 20. The imaging microscope of claim 17 wherein thebeam source emits a temporally coherent second illumination beam that isdirected at the sample, the second illumination beam having a secondwavelength that is within the mid-infrared range and that is differentthat the first wavelength.